The police and security services believe the plotters planned to launch an improvised explosive device at Downing Street - where the premier lives - and then kill Mrs May in the ensuing chaos, Sky said.

Such is the seriousness of the plot that the director general of MI5, Britain's domestic security agency, briefed Cabinet ministers on the plot, Sky said.

It said the plot was foiled with the arrest last week of two men by armed policemen.

London police said the two men arrested last week had been charged with terrorism offences and appeared in Westminster Magistrates' Court yesterday.

They were identified as Naa'imur Zakariyah Rahman, 20, of London, and Mohammed Aqib Imran, 21, of Birmingham. - REUTERS